1. Field of the Invention
The present invention relates to a contactless power transmitting device that includes a power transmitting circuit and a power receiving circuit which are both electromagnetically coupled by a transformer and can charge a secondary battery by utilizing an output electric power of the power receiving circuit
2. Related Art
As shown in FIG. 8, a device including an alternating current/direct current (AC/DC) converter 1, a power transmitting circuit 2, a transformer 5 having a primary coil 3 and a secondary coil 4, a power receiving circuit 6 and a secondary battery 7 is known as a kind of contactless power transmitting device. Further, the primary coil 3 and the second coil 4 that are included in the transformer 5 are used by approaching each other so as to be electromagnetically coupled when the secondary battery 7 is charged. After use, they can easily and physically be separated. (For example, refer to Japanese Unexamined Patent Publication Nos. 10-23677 and 2002-272020).
In the contactless power transmitting device configured in this way, the AC/DC converter 1 converts an alternating voltage to a direct current voltage. The power transmitting circuit 2 produces the alternating voltage having a predetermined frequency by utilizing the direct current voltage from the AC/DC converter 1 so as to supply the produced alternating voltage to the primary coil 3. An alternating current is induced by the alternating voltage supplied to the primary coil 3 in the secondary coil 4, the alternating current induced in the secondary coil 4 is supplied to the power receiving circuit 6. The power receiving circuit 6 rectifies the alternating current induced in the secondary coil 4 to the direct current voltage so as to be output. The secondary battery 7 is charged by the direct current voltage.
As above-mentioned, in the conventional contactless power transmitting device shown in FIG. 8, the primary coil 3 and the second coil 4 included in the transformer 5 are used by approaching each other when the secondary battery 7 is charged. After charging is complete, both can be easily physically separated. Therefore, it is convenient to use the conventional contactless power transmitting device as a power supply (secondary battery) for cellular phones and portable personal computers.
Meanwhile, cellular phones are remarkably spreading in popularity. Unfortunately, a cellular phone cannot be used after it runs out of power (loses the charge in its power supply). This often occurs when a user is away from his or her office. The conventional contactless power transmitting device cannot cope easily and promptly with this situation.
In addition to cellular phones, portable computers are also remarkably spreading in popularity. The number of businessmen and the like carrying both when they are away from their office is increasing. Notably, cellular phones have a smaller power supply capacity than that of portable computers.
Thus, when the power supply charge for the cellular phone is exhausted, it would be extremely convenient to charge the power supply of the cellular phone by utilizing the power supply for a portable computer, which could easily and promptly cope with the situation.
It should also be noted that in the conventional contactless power transmitting device, the secondary battery 7 is charged by bringing the primary coil 3 and the secondary coil 4 in the transformer 5 toward each other as above mentioned. Thus, the device offers convenience for use as a power supply for cellular phones, portable computers, or the like.
However, in the case in which the power transmitting circuit 2 starts operation in conditions where the coils 3 and 4 are next to each other, if the power transmitting circuit 2 and the power receiving circuit 6 are mismatched in specifications or the like, proper operation is not performed between the power transmitting circuit 2 and the power receiving circuit 6, thereby causing defects and the like. This is not preferable from a safety point of view.
Taking the aforesaid situation into account, if a power supply for cellular phones or the like runs out when a user is away from his or her office and the power supply is charged without contact, the present invention firstly aims to provide a contactless power transmitting device that can easily and promptly be charged at the place where the user is located.
In addition, taking the aforesaid situation into account, if a power supply for cellular phones, portable computers or the like runs out and the power supply is charged without contact, the present invention secondly aims to provide a contactless power transmitting device that can achieve an improvement in safety and fraud prevention in the charging operation.
Further, if a power supply for cellular phones or the like runs out when a user is away from his or her office and the power supply is charged without contact, the present invention thirdly aims to provide a contactless power transmitting device that can perform the charging easily and promptly, and achieve an improvement in safety and fraud prevention in the charging operation at the place where the user is located.